In lightwave communications, an optical transmitting device such as a laser or LED is connected to an optical fiber by directly butting the fiber to the active device, using lenses or mirrors to collect light from the laser or LED for transfer to the next stage, or by using an intermediate lightguide mechanism to collect the light from an active device and guide it to the fiber and take the light from the fiber for guiding it to the device which is to receive the optical data. Where a multifiber connector is used and the active device includes an array of optical fibers, an intermediate ferrule is typically used to align and mate the active sending device to a connector installed at the end of the optical fiber connector. The active device may be a light sending or receiving means. A ferrule is a block of plastic or glass with minute holes or light pipes extending through the block for conducting light from one end of the block to the other. The minute holes or light pipes of the light guide are intended to align optical fibers of ferrules in devices which are to be mated for transfer of optical data.
Optical fiber connectors having multiple fibers are known in the art. Such multi-fiber connectors are increasingly necessary as greater bandwidth applications are needed.
Multifiber connectors such as that in U.S. Pat. No. 5,214,730 show optical fiber ferrules formed by a pair of multifiber optical connector plugs having spring members for pressing the plugs toward each other in a direction axial to direction of ribbon cable inserted into the connectors. Guide pins are generally employed for aligning the multifiber optical connector plugs in an attempt to mate the ends of the individual fibers in arrays of optical fibers against one another to ensure good optical coupling, and hence effective transmission.
Generally, the array of fibers are mounted in V-grooves (U.S. Pat.No. 4,753,515) which are etched in a silicon material in order to provide for precision positioning of the fibers. Precision positioning of the fibers in the silicon block is imperative so that when two connectors are mated, the fibers align as closely as possible in order to limit any signal loss.
A typical fiber optic connector ferrule is shown in from U.S. Pat. No. 5,809,191, Stevens et al. It shows a single molded piece ferrule for receiving a multifiber cable of ribbon to provide at an open face of the ferrule having holes through which optical fibers pass. Guide pins extend parallel to one another from the ferrule for insertion into another ferrule for receiving guide pins in guide pin recesses.
Etched V-grooves can be put down with good precision, but it is difficult to bond them together and polishing them is also problematic. This results in a terminated ferrule having brittle surfaces and edges.
Another solution to alignment of optical fibers is shown in U.S. Pat. No. 5,664,039 by Grindersiev, where an array of optical fibers is held in grooves in a ferrule, and then these fibers are clamped into grooves with a second flat (ungrooved) ferrule member so fibers can be held precisely in the grooves. According to Grindersiev, this allows transmission through the connector with minimal fiber misalignment, since grooves hold the fibers securely. Grindersiev also teaches other a means for optimizing data transmission by using various designs for securing fibers in grooves through alternative designs of grooves--V-shaped, semicircular, etc.
Another method for improving alignment of optical fibers in an MT style ferrule is shown in Shiflett, U.S. Pat. No. 5,619,604. It teaches a guide prong for pre-alignment of the ferrule within a receptacle and a groove on that guide prong for mating with a rib of the receptacle.
There exists a long felt need in the art for fiber optic connectors which achieves the result of machining with high precision and accuracy in the submicron range to hold individual fibers of a fiber optic array in registration with both a ferrule in which its ribbon cable is inserted as well as a ferrule to which it will be mated with aligning guide pins.
The prior art (for example, Grindersiev) teaches improving alignment of optical fibers in two optical connectors through improvement of alignment of the fibers within a single ferrule. Other prior art solutions, Shiflett, U.S. Pat. No. 5,619,604, solve the problem of ferrule alignment by adding mechanisms to the ferrule; this not only increases the cost and complexity of a connector, but also adds an opportunity for error in the machining of additional components, such as those taught in Shiflett, U.S. Pat. No. 5,619,604.
A prudent solution to the problem of aligning optical fibers in connecting MT ferrules has evaded the prior art, but would be very beneficial to the fiber optic industry.